Scroll wheel



April 30, 1929. l E A CHASE 1,711,042

SCROLL WHEEL Filed July l2., 1926 Patented Apr. 30, 1929.

N UNITED STATES ELROY A. CHASE, OF NORTHFIELD, VERMONT.

SCROLL WHEEL.

Application led July 12,

rlhis invention relates to a grinding Wheel having grinding;l membersoi' a general Scrolllile form. The scroll type of Wheel has beenheretofore commonly used for grinding flat surfaces on blocks of graniteand other similar material and it is the general object oli my inventionto improve the construction et such scroll Wheels to the end that theymay be more etlectively adapted to certain special grinding operations.

It is more specilic object ot my invention to provide a Scroll Wheelwhich will be particularly adapted to grinding blocks oi' granite havingsurfaces which are curved in one section and straight orilat in aSection perpendicular thereto. Such blocks are commonly but somewhatinaccnrately termed oval tops in the stone polishing trade.

ln grinding such curved surfaces, the grinding Wheel makes only a linecontact vvith the stone and the Wear of the Wheel is quite differentfrom that which occurs in grinding a Hat surface. The amount of surl'aceto be ground with line contact is substantiallythe same at all radialdistances from the axis of the Wheel, While the area ot' the grindingsurface or the Wheel commonly increases with the radial distance .fromthe axis and the outer portions of the wheel are also rotating at muchincreased speed.

A For this reason, oval tops7 have com-` monly been produced by otherand more expensive methods such as the use ot surface cutters.Vilhcnever any one attempted to use the ordinary scroll or ring wheel onoval top Work, the wheel had a strong' tendency to become concave ordished at the center and the Work was apt to be corresponding'ly roundedor convex Where it should be iflat.

It is a further object of my invention to provide a scroll wheel sodesig'nl-d as to substantially equalize the wear at diilerent radialdistances Jfrom the axis ot the. Wheel. thereby preserving the flatgrinding Surface olf the wheel. To the attainment ot this object, lprovide a design ttor the scroll member-s which substantially increasesthe area or grindingl surface toward the center o'l the. Wheel.otlfsettinc' the greater circumference and higher speed at theperiphery.

A tui-ther feature of the invention relates to the provision ot a seriesot pockets in the inner Walls of Scroll members ot the type 1926. SerialNo. 121,765.

described, by which provision the efficiency of the Wheel is stillfurtherincreased.

My invention further relates to arrange` ments and combinations of partswhich will be hereinafter described and more particularly pointed out inthe-appended claims.

Preferred forms of `the invention are shown in the drawings in which y iFig. 1 is a bottom view oit ascroll Wheel embodying one form of myinvention;

Fig; 2 is a top or plan View thereof;

F ig. 3 is a side elevation of the Wheel shown in Figs. 1 and 2, and

F 4 is a. bottom View of a. modification.

Referringr to Figs. 1 and 3, I have Shown a small scroll wheelpreferably of cast iron, and comprising two scroll members connected bya cross bar 11 and also by Spots or tyingr elements 12. The cross bar 11`is `provided with ears 13 adapted to receive a rocking member 14pivoted on a cross pin 15 in the end of a drive shaft 16. y.

The grinding;r Wheel VVthus has a swivel connection with the drive shaft1G and is held against the stone S by the direct pressure of the drivesha-ft against the ears 13.`

The Wheels may be removed and replaced by merely raising thedrive shaftout of the open bearings in the ears 13. i The scroll members 10 are ofa special shape and construction which will now be described. Theextreme outer end portion ot each member 10 iS substantially concentricWith the axis of the wheel between the points a, and b (Fig. l), or forabout a quarter of the circumference. The pio vision of these circularouter portions has been found very desirable for use on oval top work inwhich reverse curves are frequently encountered, as the cylindricalouter surfaces prevent the bumping or jarring action Which wouldotherwise occur when the edges of the scroll Wheel encountered areversed curve portion ot the surface.

Each grinding element 10 is also gradually increased in etfectivewidthas the scroll approaches the axis of the wheel. The object of thisincrease in width, as previously pointed ont7 is to equalize the Wearot' the Wheel when lgrinding a curved surface in which there is onlyline Contact, and in which the Wheel surface area operative at a tgivenpoint on the line of contact otherwise varies directly With the distancefrom the l axis. By increasing the width of the grind-` ing surface asit approaches the center, this variation in grinding action issubstantially offset and a Wheel is produced which will Wear evenly andpreserve its flat grinding face even when used on oval top Work withline contact only.

I further increase the eiliciency of my improved grinding Wheel byproviding a series of pockets or sei-rations 17 on the inner faces ofthe grinding members l0. The outer Wall 18 of each pocket is preferablysubstantially concentric with the axis of the Wheel W and thisconstruction facilitates the feed of the abrasive under the scrollshapedgrinding members. A grinding Wheel constructtal as above described hasbeen found very effective :tor the purposes indicated and is adapted totake the place of the much more expensive surface cutting operationwhich has been commonly used for producing curved or ov: l top surfaces.

In Fig. 4, I have shown a wheel having a single continuous scroll memberbut otherwise of the construction previously described. This Wheel mayalso be provided with pockets as in the form shown in Figs. l to 3.

l Having thus described my invention and the advantages thereof, I donot wish to be limited to the details herein disclosed otherwise than asset forth in the claims, but what I claim is l. A Wheel for grindingStone having a. scroll-shaped grinding member, the grinding surface ofwhich is gradually increased throughout the length of the scroll as saidscroll member approaches the axis of the Wheel.

2. A Wheel for grinding stone having a scroll-shaped grinding member inwhich the average effective Width of grinding surface is constantlyincreased throughout the length of the scroll toward the axis of theWork.

3. A. wheel tor grinding stone having scroll-shaped grinding members inwhich the grinding surface ol' said members is increased in Widththroughout the length ot the scroll toward the axis ot the Wheel, and inwhich the inner side faces of said memw bers are serrated.

t. A Wheel for grinding stone having a scroll-shaped grinding member7the grinding surface of vwhich is gradually increased throughout thelength. of the scroll as said scroll member approaches the axis ol theWheel, and in which Wheel thc eXtreme outside portion of said memberforms substantially the segment ol" a cylinder.

5. A wheel tor grinding stone having` scrollshaped grinding members, thegrinding surfaces oit which are graulually increased throughout thelength of the scroll as said scroll members apijiroacn the axis ot theWheel, and in which pockets are pro- `-ided in the inner t'aees oi saidmembers, the outer Walls ol said pockets being substantially concentricwith the axis ot' said Wheel.

6. A wheel for grinding stone, comprising a plurality oit imlepeudentscroll shaped grinding members tied together by a crossbar, the grindingsurfaces of each of said members being gradually increased throughoutthe length of thescroll as the members approach the axis of the Wheelformed by the members.

In testimony whereof I have hereunto ailixed my signature.

ELROY A. CHASE.

